how to troubleshoot P0304 code in Toyota Corolla E170 (2013-2019)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Toyota Corolla E170 (2013-2019). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative terminal of the battery to ensure safety.
• Allow the engine to cool completely before starting work.

2. Inspect and Replace Spark Plug

• Remove the ignition coil from cylinder 4:
  • Unplug the electrical connector from the ignition coil.
  • Remove the retaining bolt using a socket set.
  • Gently pull the ignition coil out.
• Remove the spark plug from cylinder 4:
  • Use a spark plug socket to unscrew and remove the spark plug.
  • Inspect the spark plug for wear, fouling, or damage.
• Replace the spark plug if necessary:
  • Gap the new spark plug according to manufacturer's specifications.
  • Install the new spark plug and torque to the required specification (typically 13-16 ft-lbs).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Inspect and Replace Ignition Coil (if needed)

• If the ignition coil shows signs of failure (cracks, discoloration), replace it:
  • Follow the steps from "Remove the ignition coil" and install a new ignition coil.
  • Torque the ignition coil retaining bolt to the manufacturer's specification.

4. Fuel Injector Inspection

• Test the fuel injector for cylinder 4:
  • Disconnect the fuel injector connector.
  • Use a multimeter to check the resistance of the injector (specification usually around 12-16 ohms).
• If the injector is faulty, replace it:
  • Remove the intake manifold if necessary to access the fuel rail.
  • Disconnect the fuel lines and remove the fuel rail with injectors.
  • Replace the faulty injector with a new one and reassemble.

5. Compression Test

• Perform a compression test on cylinder 4:
  • Remove the spark plug and insert the compression gauge into the cylinder.
  • Crank the engine and record the compression reading.
• Compare the reading to manufacturer specifications; if low, further diagnosis of engine internals may be required.